NASA's Hubble Space Telescope has discovered a new great dark spot,
located in the northern hemisphere of the planet Neptune. Because the
planet's northern hemisphere is now tilted away from Earth, the new
feature appears near the limb of the planet.

The spot is a near mirror-image to a similar southern hemisphere dark
spot that was discovered in 1989 by the Voyager 2 probe. In 1994,
Hubble showed that the southern dark spot had disappeared.

Like its predecessor, the new spot has high altitude clouds along its
edge, caused by gasses that have been pushed to higher altitudes where
they cool to form methane ice crystal clouds. The dark spot may be a
zone of clear gas that is a window to a cloud deck lower in the
atmosphere.

Planetary scientists don t know how long lived this new feature might
be. Hubble's high resolution will allow astronomers to follow the
spot's evolution and other unexpected changes in Neptune's dynamic
atmosphere.

The image was taken on November 2, 1994 with Hubble's Wide Field
Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion
kilometers) from Earth. Hubble can resolve features as small as 625
miles (1,000 kilometers) across in Neptune's cloud tops.